System and method for retrograde procedure

ABSTRACT

A system and method may be used for accessing an articular surface and for preparing an implant site on the articular surface. The method may include locating a portion of the articular. An access passage may be drilled towards the articular surface though bone behind the articular surface. An implant site may be excised in the articular surface relative to an axis defined by the access passage.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional patent application Ser. No. 60/603,473, filed Aug. 20, 2004. This application is also a continuation in part of U.S. patent application Ser. No. 11/169,326, filed Jun. 28, 2005, which claims the benefit of U.S. provisional patent application Ser. No. 60/583,549, filed Jun. 28, 2004. This application is also a continuation in part of U.S. patent application Ser. No. 10/994,453, filed Nov. 22, 2004. Additionally, this application is also a continuation in part of U.S. patent application Ser. No. 10/308,718, filed Dec. 3, 2002. Then entire disclosures of all of the above listed applications are incorporated herein by reference.

FIELD

The present disclosure is directed at a system and method for accessing an articular joint surface. The present disclosure is further directed at a method and system for replacing at least a portion of an articular surface.

BACKGROUND

Articular cartilage, found at the ends of articulating bone in the body, is typically composed of hyaline cartilage, which has many unique properties that allow it to function effectively as a smooth and lubricious load bearing surface. Hyaline cartilage problems, particularly in knee, hip joints, and should joints, are generally caused by disease such as occurs with rheumatoid arthritis or wear and tear (osteoarthritis), or secondary to an injury, either acute (sudden), or recurrent and chronic (ongoing). Such cartilage disease or deterioration can compromise the articular surface causing pain and eventually, loss of joint movement. As a result, various methods have been developed to treat and repair damaged or destroyed articular cartilage.

For smaller defects, traditional options for this type of problem include leaving the lesions or injury alone and living with it, or performing a procedure called abrasion arthroplasty or abrasion chondralplasty. The principle behind this procedure is to attempt to stimulate natural healing. The bone surface is drilled using a high speed rotary burr or shaving device and the surgeon removes about 1 mm of bone from the surface of the lesion. This creates an exposed subchondral bone bed that will bleed and will initiate a fibrocartilage healing response. One problem with this procedure is that the exposed bone is not as smooth as it originally was following the drilling and burring which tends to leave a series of ridges and valleys, affecting the durability of the fibrocartilage response. Further, although this procedure can provide good short term results, (1-3 years), fibrocartilage is seldom able to support long-term weight bearing and is prone to wear, soften and deteriorate.

Another procedure, called Microfracture incorporates some of the principles of drilling, abrasion and chondralplasty. During the procedure, the calcified cartilage layer of the chondral defect is removed. Several pathways or “microfractures” are created to the subchondral bleeding bone bed by impacting a metal pick or surgical awl at a minimum number of locations within the lesion. By establishing bleeding in the lesion and by creating a pathway to the subchondral bone, a fibrocartilage healing response is initiated, forming a replacement surface. Results for this technique may be expected to be similar to abrasion chondralplasty.

Another means used to treat damaged articular cartilage is a cartilage transplant. Essentially, this procedure involves moving cartilage from an outside source or other knee or from within the same knee into the defect. Typically, this is done by transferring a peg of cartilage with underlying bone and fixing it in place with a screw or pin or by a press fit. Although useful for smaller defects, large defects present a problem, as this procedure requires donor pegs proportionate to the recipient bed. Large diameter lesions may exceed the capacity to borrow from within the same knee joint and rule out borrowing from another source.

Larger defects, however, generally require a more aggressive intervention. Typically treatment requires replacing a portion or all of the articular surface with an implant or prosthetic having an outer layer that that is polished or composed of a material that provides a lubricious load bearing surface in approximation of an undamaged cartilage surface. Replacement of a portion, or all, of the articular surface requires first cutting, boring, or reaming the damaged area to remove the damaged cartilage. A recess to receive an implant or prosthetic is formed at the damaged site. The implant or prosthetic is then secured to the bone in an appropriate position in the recess.

The treatment and/or replacement procedure often requires direct access to the damaged surface of the cartilage. While the most commonly damaged portions of some joints may easily be accessed for repair using a minimally invasive procedure some joints are not nearly as accessible. For example, the superior or medial femoral head, the medial humeral head, the glenoid, etc. do not permit direct access sufficient to carry out replacement of the articular surface in a minimally invasive manner. In fact, repair of such obstructed joints often requires an invasive procedure and necessitates complete dislocation of the joint. Procedures of such an invasive nature may be painful and require an extended recovery period.

Accordingly, it is an object of the present invention to provide a method for replacing an articular joint surface that is obscured from axial approach that is less invasive than conventional procedures and may not necessitate completely dislocating the joint.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the present disclosure is set forth by description of embodiments consistent therewith, which description should be considered in combination with the accompanying drawings, wherein:

FIG. 1 illustrates an embodiment of a retrograde articular surface replacement system consistent with the present disclosure;

FIG. 2 illustrates the use of the retrograde articular surface replacement system of FIG. 1 to position a guide pin in a bone;

FIG. 3 shows a fixation element positioned below an articular surface using a retrograde articular surface replacement system according to the present disclosure;

FIG. 4 is a cross-sectional view of the retrograde articular surface replacement system depicted in FIG. 3;

FIG. 5 is an enlarged cross-sectional view of a portion of the retrograde articular surface replacement system of FIG. 4 adjacent a locating hoop thereof;

FIG. 6 is an enlarged cross-sectional view of a portion of a retrograde articular surface replacement system consistent with the present disclosure including a depth probe

FIG. 7 is a representational cross-sectional view of an articular surface having an implant installed therein using a retrograde articular surface replacement system according to the present disclosure;

FIG. 8 is a perspective view of a retrograde articular surface replacement system consistent with the present disclosure applied to an articular surface of a femoral head;

FIG. 9 is an enlarged view of a portion of the articular surface replacement system of FIG. 8 adjacent the articular surface of the femoral head;

FIG. 10 is a perspective view of an embodiment of the articular surface replacement system in use to replace a cooperating articular surface consistent with the present disclosure;

FIG. 11 illustrates an implant site excised in a cooperating articular surface consistent with the present disclosure;

FIG. 12 depicts an articular surface implant installed in a cooperating articular surface; and

FIG. 13 is a cross-sectional view of the articular surface of FIG. 12.

DESCRIPTION

By way of overview, the present disclosure provides a retrograde articular surface replacement system that may include a method and apparatus for replacing at least a portion of an articular surface including accessing a desired portion of the articular surface through a portion of bone. While the preceding overview and the following specific embodiments of the system according to the present disclosure are directed at a system for replacing at least a portion of an articular surface, the system herein may be used in connection with procedures other than the replacement of portions of an articular surface. From a broad standpoint, the system disclosed herein may provide an apparatus and method for accessing a bone, joint, etc., indirectly.

Turning to FIG. 1, an embodiment of a retrograde articular surface replacement system 10 is illustrated. The system 10 may generally include a locating device, such as locating hoop 12, coupled to a guide, such as a cannulated shaft 18. The locating hoop 12 and the cannulated shaft 18 may be maintained in a positional and angular relationship by an arm 16. Consistent with the illustrated embodiment, the cannulated shaft 18 may be coupled to a tool support 14, and the tool support 14 may be coupled to the locating device 12 by an arm 16. The locating hoop 12 and the cannulated shaft 18 may be positioned in an opposed arrangement around a bone 20 having an articular surface 22.

The locating hoop 12 may include an opening there through such that when the locating hoop 12 is disposed on the articular surface 22 a portion of the articular surface may be exposed through the opening of the locating hoop 12. Furthermore, when the locating hoop 12 is disposed on the articular surface 22 the locating hoop 12 may achieve a desired orientation relative to a portion of the articular surface 22 exposed through the opening of the locating hoop 12. According to the illustrated embodiment, the locating hoop 12 may generally be configured as a ring having a circular opening extending therethrough. As shown, the locating hoop 12 may be positioned on an articular surface 22. According to one embodiment, when the locating hoop 12 is positioned on the articular surface 22 the locating hoop 12 may be oriented such that the axis of the opening of the locating hoop 12 may be generally normal to the articular surface 22 at the point of intersection by the axis of the opening. According alternative embodiments, the locating hoop 12 may achieve various other desired orientations relative to the articular surface 22.

The tool support 14 may include an opening 24 extending inwardly from a rear portion 26 of the tool support 14. The tool support 14 may define one or more windows 28 to the opening 24. According to one embodiment, the window 28 may include a transparent region of the tool support 14. For example, the window 28 may include a transparent plastic, glass, etc. region allowing the interior of the opening 24 to be viewed. Alternatively, the window 28 may be provided as an opening in a side region of the tool support 14. In such a configuration, the window 28 may not only allow the interior of the opening 24 to be viewed, but may also allow the interior of the opening 24 to be accessed and/or allow tools and/or objects within the opening 24 to be manipulated from the exterior of the tool support 14.

The tool support 14 may also include a bore 30 extending from the opening 24 to a front region of the tool support 14. As shown, the bore 30 may be sized to receive the cannulated shaft 18 therethrough. According to one embodiment, the inside diameter of the bore 30 may be closely sized to the outside diameter of the cannulated shaft 18 to maintain the cannulated shaft 18 in substantially coaxial alignment with the bore 30. Additionally, the tool support 14 may include a locking mechanism 32 that may be engaged to resist axial and/or rotational movement of the cannulated shaft 18. Suitable locking mechanisms 32 may have a variety of configurations. For example, the locking mechanism 32 may be a frictional locking mechanism including a bearing member that may press against, and frictionally engage, the cannulated shaft 18. Another suitable locking mechanism 32 may include a plurality of teeth that may be selectively engaged with corresponding features, such as circumferential grooves/ridges on at least a portion of the exterior of the cannulated shaft 18. Various other locking mechanisms may also, or alternatively, be employed herein.

The locating hoop 12 and the tool support 14 may be coupled to one another by an arm 16. The arm 16 may maintain the locating hoop 12 and the tool support 14 in a desired angular alignment and or position relative to one another. For example, the arm 16 may orient the locating hoop 12 and the tool support 14 such that the axis of the bore 30 intersects the center of the opening of the locating hoop 12 at a desired angle. The arm 16 may also arrange the tool support 14 and locating hoop 12 in predetermined relative angular alignments in which the axis of the bore 30 does not intersect the opening of the locating hoop 12. According to one embodiment, the locating hoop 12 may be oriented perpendicular to the guide shaft 18.

Consistent with the illustrated embodiment, the arm 16 may be a compound arcuate member having a fixed geometry. Accordingly, the relationship between the locating hoop 12 and the tool support 14 may be fixed relationship. It is contemplated herein, however, that the arm 16 may be releasably coupled to the tool support 14 and/or the locating hoop 12. In such an embodiment the tool support 14 and/or the locating hoop 12 may be separated from the arm 16. The arm 16 may be replaced with another arm, or arm 16 and locating hoop 12 assembly, providing a different configuration and/or providing a different angular alignment and or positional relationship between the locating hoop 12 and the tool support 14. According to a related embodiment, the arm 16 may be provided as an adjustable feature, thereby allowing the angular alignment and/or positional relationship between the locating hoop 12 and the tool support 14 to be varied or modified without replacing the arm 16.

Consistent with the illustrated embodiment, the cannulated guide shaft 18 may generally include a proximal receptacle portion 33, a shaft portion 34, and a distal tip 36. The shaft portion 34 may include at least one lumen extending along the length of the cannulated shaft 18. At least a portion of the shaft 34 may be disposed in the bore 30 of the tool support 14. Desirably, the shaft 34 is sized with respect to the bore 30, to provide a minimal of clearance. Accordingly, positioning the shaft portion 34 at least partially within the bore 30 may align an axis of the lumen in a predetermined relationship relative to the axis of the bore 30. As previously discussed, the bore 30 may in turn be oriented in a predetermined angular and/or positional arrangement relative to the locating hoop 12. The locating hoop 12 may itself be arranged in a predetermined relationship to the articular surface 22. Accordingly, when the shaft 34 is at least partially disposed within the bore 30 the lumen of the shaft portion 34 may be arranged in a desired angular and/or positional orientation relative to the opening of the locating hoop 12. In one embodiment, the axis of the lumen may be oriented parallel to the axis of the bore 30 when the shaft portion 34 is at least partially received in the bore 30. In a further embodiment, the lumen may be oriented coaxial with the bore 30 when the shaft portion 34 is at least partially received in the bore 30.

With additional reference to the cross-sectional view of FIG. 4, the receptacle portion 33 of the cannulated shaft 18 may include a cupped or conical interior profile leading to the lumen of the cannulated shaft 18. The cupped or conical receptacle portion 33 may facilitate the insertion of instruments, devices, etc. into the lumen of the cannulated shaft 18. Consistent with the preceding aspects, instruments, devices, etc. inserted into the lumen with the aid of the cupped or conical receptacle portion 33 may be at least generally oriented in a predetermined relationship to the opening of the locating hoop 12 by virtue of the orientation of the lumen relative to the opening of the locating hoop 12. Accordingly, instruments, devices, etc. may be at least generally placed in a predetermined orientation and/or alignment relative to a portion of the articular surface 22 identified within the locating hoop 12.

As shown in the FIG. 1, the locating hoop 12 may be positioned around a desired portion of the articular surface 22. The cannulated shaft 18 may then be inserted extending through the bore 30 of the tool support 14. The cannulated shaft 18 may be positioned so that the distal tip 36 of the cannulated shaft 18 may bear against the bone 20 opposite the articular surface 22 in the predetermined alignment relative to the opening of the locating hoop 12. As in the illustrated arrangement, when the locating hoop 12 and the distal tip 36 of the cannulated shaft 18 are positioned to bear on opposing sides of the bone 20, the distal tip 36 of the cannulated shaft 18 may contact the bone 20 at an angle. In such an orientation, only a portion of the distal tip 36 may actually contact the bone 20. The partial contact between the distal tip 36 and the bone 20 may make the distal tip 36 susceptible to moving across the surface of the bone 20, and therein altering the position of the locating hoop 12 on the articular surface 22.

Movement of the distal tip 36 of the cannulated shaft 18 across the surface of the bone 20 may be reduced by providing the distal tip 36 having biting features. For example, as shown the tip 36 may have a serrated or saw tooth end feature. When the distal tip 36 is pressed against the bone 20, the serrated end feature may engage the bone 20 and resist movement once the tip 36 is so engaged. Accordingly, the system 10 may be placed in a desired position and/or alignment relative to the articular surface 22 by positioning the bone between the locating hoop 12 and the distal tip 36 of the cannulated shaft 18. The locating hoop 12 and distal tip 36 may be brought to bear on opposing sides of the bone 20. The cannulated shaft 18 may then be locked in position using the locking mechanism 32 of the tool support 14. Accordingly, it may be possible to maintain the system 10 in the desired position and/or alignment relative to the articular surface even when the desired position causes the distal tip 36 of the cannulated shaft 18 to contact the bone at an angle such that only a portion of the distal tip 36 contacts the bone 20.

Turning to FIG. 2, a system 10 consistent with FIG. 1 may be used in a procedure for replacing a portion of an articular surface 22. According to an embodiment of the procedure consistent with the present disclosure, once the locating hoop 12 and the cannulated shaft 18 are oriented in a desired alignment relative to the articular surface 22, a reference axis may be established relative to the articular surface 22. According to one embodiment, establishing the reference axis may include providing a passage or hole through the bone 20. The passage or hole may pass all the way through the bone 20 and exit the articular surface 22. This may allow the alignment and orientation of the reference axis relative to the articular surface 22 to be verified.

A reference axis may be established, consistent with the present disclosure, by drilling a hole through the bone 20 in a predetermined alignment relative to the cannulated shaft 18. According to one embodiment, the hole may be aligned coaxially with the cannulated shaft 18. Consistent with the present disclosure, the hole for the reference axis may be relatively small diameter compared to the lumen of the cannulated shaft 18. The reference axis hole may be drilled in the desired alignment using a reducer shaft 38. The reducer shaft 38 may be a cannulated shaft having an outside diameter sized to be received within the lumen of the cannulated shaft 18. The inside diameter of the lumen of the reducer shaft 38 may be sized to receive and align a pilot drill bit for drilling a reference axis hole having the desired diameter. Similar to the cannulated shaft 18, the reducer shaft 38 may include a cupped or conical proximal receptacle 40. The cupped or conical receptacle 40 may facilitate aligning instruments, tools, and/or other devices with the lumen of the reducer shaft 38, and/or inserting such instruments, tools, and/or other devices into the lumen of the reducer shaft 38.

With the locating hoop 12 and cannulated shaft 18 aligned and locked in a desired orientation relative to the articular surface 22, the reducer shaft 38 may be inserted into the lumen of the cannulated shaft 18 via the opening 24 in the rear of the tool support 14. The reducer shaft 38 may extend through at least a portion of the lumen of the cannulated shaft 18. According to one embodiment, the reducer shaft 38 may extend through the cannulated shaft 18 and contact the bone 20 or terminate proximate the surface of the bone 20. In such a configuration, the instruments, tools, etc., such as the pilot drill bit, may be fully supported up to the surface of the bone 20.

With the reducer shaft 38 in position within the lumen of the cannulated shaft 18, a guide pin 42 may be loaded through the opening 24 of the tool support 14 and into the lumen of the reducer shaft 38. Loading the guide pin 42 into the lumen of the reducer shaft may be facilitated by the cupped or conical receptacle 40 of the reducer shaft 38. The guide pin 42 may include a drill tip (not shown) or other cutting feature disposed on a distal end of the guide pin 42. The guide pin may be driven, e.g., by a drive motor or manual drive handle, from the rear portion 26 of the tool support 14. The depth of the hole may be gauged by observing penetration of the guide pin 42 through the articular surface 22 within the opening of the locating hoop 12. Alternatively, the separation between the tool support 14 and the locating hoop 12 may be known based on the configuration of the arm 16, locating hoop 12, and tool support 14. In one embodiment, the guide pin 42 may be provided having indicia representative of depth of penetration. The depth of the reference axis hole may be determined from the relationship between the guide pin 42 and at least one of the tool support 14, the reducer shaft 38 and the cannulated shaft 18, etc.

After the guide pin 42 has been drilled into and/or through the bone 20 in the above described manner, the guide pin 42 may be maintained extending into/through the bone and/or articular surface 22. The guide pin 42 extending at least partially into or through the bone 20 may provide a reference axis aligned through the reducer shaft 38. The guide pin 42 may be used locate subsequent operations and/or instruments relative to the reference axis. Once the guide pin 42 has been positioned in the hole through the bone 20, the reducer shaft 38 may be withdrawn from the lumen of the cannulated shaft 18. At least a portion of the guide pin 42 may remain in the hole extending into the bone 20. If the guide pin 42 is provided with a close fit with the hole, the guide pin 42 may be maintained in a desired alignment with the reference axis.

According to an alternative embodiment, a drill may be used to provide a hole extending into and/or through the bone 20. The reducer shaft 38 may be used to align and/or support the drill bit during the drilling operation. After the hole has been drilled extending into or through the bone 20, a guide pin 42 may be inserted extending into or through the hole to provide a reference axis, in a similar manner to the preceding description.

After the guide pin 42 has been positioned extending from the bone 20 in a desired position relative to the reference axis, a larger hole may be drilled into the bone for receiving a fixation and/or location element. Consistent with one embodiment, the hole for the fixation element may extend all of the way through the bone 20 and the articular surface 22. In other embodiments, however, the hole for the fixation element may extend only partially through the bone 20.

In one embodiment, the hole or tunnel for the fixation element may be drilled at least part of the way through the bone 20 using a cored drill. That is, the drill may include a lumen, or opening therethrough. The lumen through the drill may be sized to receive the guide pin 42. With the guide pin 42 received through the lumen of the drill, the hole for the fixation element may be drilled into the bone 20 with the drill carried on/supported by the guide pin. Carrying the drill on the guide pin 42 in this manner may allow the hole for the fixation element to be provided in a desired alignment relative to the reference axis through the articular surface 22. Additionally, carrying the drill on the guide pin 42 may, for example, eliminate the need for an additional reducer tube to support the drill on the outside diameter thereof in a situation in which the outside diameter of the drill is less than the inside diameter of the lumen of the cannulated shaft 18. Alternatively, or additionally, a reducer tube supporting the outside diameter of the drill may be used for drilling the hole.

Turning next to FIGS. 3 and 4, after a hole or tunnel has been drilled through the bone 20 for a fixation element, the fixation element may be positioned within the bone. Consistent herewith, the fixation element may be an element adapted to retain, or assist in retaining, an implant to the bone 20. In the illustrated embodiment, the fixation element is configured as a screw 44. According to one embodiment, the screw 44 may be delivered to the bone 20 through the cannulated shaft 18. The outside diameter of the screw 44 may, therefore, be smaller than the inside diameter of the lumen of the cannulated shaft 18, thereby allowing the screw to be passed from the tool support 14 and through the cannulated shaft 18. The hole through the bone 20 for receiving the screw 44 may have a diameter smaller than the outside diameter of the threads of the screw 44 to allow the threads of the screw 44 to engage the bone 20. Various other elements or features may additionally or alternatively be used as fixation elements.

Consistent with the illustrated embodiment, the screw 44 may be rotatably driven, i.e., screwed, into the bone using a probe-driver 46. The probe-driver 46 may include a shaft 48 that is configured to extend through the lumen of the cannulated shaft 18. A distal region of the shaft 48 may be provided having a feature for engaging and/or driving the screw 44. For example, the shaft 48 may include a hexagonal region that is adapted to be received by a corresponding hexagonal socket, or opening, in the screw 44. Various other features and configurations may be utilized to permit the shaft 48 to engage and/or drive the screw 44.

The probe-driver 46 may also include a knob 50 coupled to the proximal end of the shaft 48. The knob 50 may be coupled to the shaft 48 in a torsionally stiff manner such that rotating the knob 50 may also rotate the shaft 48 to drive the screw 44. Additionally, the probe-driver may include a cylindrical region 52 that may be sized to be rotatably received in the opening 24 of the tool support 14. According to one embodiment, the cylindrical region 52 may be sized relative to the opening 24 so that the probe-driver 46 may be supported by the opening 24 of the tool support 14.

Consistent with one embodiment, the cylindrical region 52 of the probe-driver 46 and the tool support 14 may include cooperating indicia (not shown) representative of the depth of penetration of the cylindrical region 52 into the opening 24 of the tool support 14. According to one embodiment, the indicia may be correlated to depth of insertion of the screw 44 into the bone 20. Accordingly, the depth of installation of the screw 44 into the bone 20 can be controlled and/or ascertained. The cooperating indicia may include, for example, a graduated scale and a reference, a vernier scale, or other system of reference marks.

Consistent with a particular embodiment, the indicia may be correlated to the depth of the screw 44 beneath the articular surface 22. Such a correlation may be achieved based on the known distance between the articular surface 22, as established by the locating hoop 12, and the tool support 14 which is established by the arm 16. Using a screw 44 having a known length and a predetermined seating height of the screw on the shaft 48 of the probe-driver 46, it may be possible to drive the screw 44 into the bone 20 to a predetermined distance from the articular surface 22.

With additional reference to FIGS. 5 and 6, the distal end of the shaft 48 may include a probe feature 54. As shown, the probe feature 54 may extend through the screw 44 and beyond the end of the screw 44 a predetermined distance. Consistent with the embodiment illustrated in FIG. 5, the probe feature 54 may be used to position the screw 44 at a predetermined depth in the bone 20 relative to the locating hoop 12. The screw 44 may be provided having a known length and may be configured to seat on the shaft 48 of the probe-driver 46 a known distance from the distal tip of the shaft 48. The known length and known seating height of the screw 44 may be based on predetermined design characteristics and/or on measurements taken prior to installation of the screw 44. Consistent with the embodiment of FIG. 5, the screw 44 may be positioned at a predetermined depth relative to the locating hoop 12 by driving the screw 44 until the probe feature 54 reaches a predetermined height relative to the locating hoop 12. For example, the screw 44 may be driven into the bone until the tip of the probe 54, at the distal end of the shaft 48 of the probe-driver 46, is flush with the top of the locating hoop 12 as shown. Various other alignment relationships between the tip of the probe 54 on the shaft 48 of the probe-driver 46 may also, or alternatively, be used for positioning the screw 44 at a desired depth within the bone 20.

In a related embodiment, illustrated in FIG. 6, the probe feature 54 of the probe-driver 46 may be used to position the screw 44 at a predetermined depth relative to the articular surface 22. For example, the screw 44 may be positioned at a predetermined depth relative to the original articular surface 22, or may be positioned at a predetermined depth relative to the articular surface 22 surrounding the hole for receiving the screw 44. According to either embodiment, a screw 44 may be provided having a predetermined length and having a predetermined seating height on the distal end of the shaft 48. The screw 44 may then be driven into the bone 20 until the probe feature 54 reaches a predetermined height relative to the articular surface 22.

Embodiments may be provided combining various aspects of the previously described cooperating indicia on the probe-driver 46 and tool support 14 and the probe feature 54 on the shaft 48 of the probe-driver 46. Such embodiments combining these aspects may be used to position the screw at a predetermined depth relative to at least one of the locating hoop 12 and the articular surface 22.

According to an alternative embodiment, the fixation element, such as screw 44 may be inserted into the bone from the articular surface 22. According to such an embodiment, after a hole has been drilled through the articular surface 22, the screw 44 may be passed to the articular surface 22 and introduced into the bole therein. For example, a line, such as a metal wire, plastic filament, etc., may be passed through the hole and the screw 44 or attached to the screw 44 and pass through the hole. The screw 44 may then be drawn to the hole in the articular surface 22. The screw 44 may then be driven into the articular surface in a manner similar to the preceding embodiment, e.g., using a drive shaft extending through the hole in the bone 20.

After the screw 44 has been installed at a desired position in the bone 20, a region of the articular surface 22 surrounding the axis of the screw 44 may be excised to provide an implant site. The articular surface 22 may be excised using a rotating cutting device that may be positioned so that the rotational axis of the cutting device may be generally aligned with the axis of the opening through the screw 44. According to one embodiment, a line, such as a metal wire, plastic filament, etc., may be passed through the bone 20 so that it extends from the articular surface 22 and from the opposed side of the bone. The wire may pass through, or be coupled to the cutting device along the rotational axis there of. The cutting device may then be drawn toward the articular surface by withdrawing the wire through the bone or by sliding the cutting device along the wire towards the articular surface. In either case, the wire passing through the bone 20 may act to align the rotational axis of the cutting device with the axis of the opening through the screw 44. Alternative methods for positioning the cutting device relative to the articular surface may also be employed consistent with the present disclosure, including manually positioning the cutting device.

According to one embodiment, the cutting device may include a socket or opening along the rotational axis of the cutting device. For example, the cutting device may include a hexagonal socket along the rotational axis of the cutting device. The socket or opening along the rotational axis of the cutting device may allow the cutting device to be rotationally driven to excise at least a portion of the articular surface. Once the cutting device has been positioned on the articular surface with the rotational axis of the cutting device generally aligned with the opening through the screw 44, a drive shaft may be inserted through the hole through the bone and the opening through the screw and may engage the cutting device. For example, in the case of a cutting device having a hexagonal socket, the drive shaft may include a hexagonal feature adapted to be received in the hexagonal socket of the cutting device.

Once the drive shaft has been engaged with the cutting device, the cutting device may be rotatably driven by the drive shaft. The drive shaft, and thereby the cutting device, may be manually driven, e.g., by rotating a handle proximal to the cutting device, or may be mechanically drive, e.g., by a drive motor or drill device. While the cutting device is being rotatably driven by the drive shaft, the cutting device may also be pulled in to the articular surface 22, thereby excising the articular surface to form a generally circular implant site.

The depth of the implant site may be controlled in a variety of manners including visual inspection of the implant site and/or the depth of the cutting device in the implant site, indicia on the drive shaft indicative of the depth the cutting device has been pulled into the articular surface, etc. According to one embodiment, the depth of the implant site may be controlled by the screw 44, or other fixation element. The screw 44 may include an upper bearing surface 56, generally in FIG. 6. The cutting device may have a corresponding lower bearing surface adjacent the screw 44. The cutting device may be rotatably driven and pulled into the articular surface 22 until the lower bearing surface of the cutting device bears against the upper bearing surface 56 of the screw 44. Accordingly, the excision site may be provided having a predetermined depth relative to the screw.

Depending upon the diameter of the implant site, the locating hoop 12 and/or the tool support 14 may be removed from the bone 20 prior to excising the implant site. For example, if the diameter of the implant site is to be equal to, or greater than, the inside diameter of the locating hoop 12, it may be desirable to remove the locating hoop from the region of the articular surface 22 to be excised prior to excising the implant site. If the diameter of the implant site, however, is to be smaller than the inside diameter of the locating hoop 12, the locating hoop 12 may optionally be maintained in position on the articular surface 22. If the locating hoop 12, tool support 14, etc., are removed during excision of the implant site, the opening extending through the screw 44 may serve as an alignment feature. That is, the diameter of the drive shaft may be dimensioned relative to the opening through the screw 44 such that the drive shaft may be maintained in a generally desired alignment by the opening through the screw 44 during excision of the implant site.

According to an alternative embodiment, the implant site may be excised prior to, or without, the installation of a fixation element such as a screw. In such an embodiment, the depth of the implant site may be provided using visual inspection, indicia on the drive shaft and/or cutting device, etc. The orientation of the excision may be controlled either by the tool support 14, e.g. via a guiding cannulated shaft or other guide feature, or by the hole through the bone. In either case the implant site may be provided in a manner as described above, with the cutting device being rotatably driven to excise a desired portion of the articular surface 22, and/or underlying bone 20.

As shown in FIG. 7, once the implant site has been excised, an implant 58 replacing at least a portion of the articular surface 22 may be installed into the implant site. A wide variety of implants and/or implants having various different characteristics may suitable be employed to replace at least a portion of an articular surface consistent with the present disclosure. Accordingly, the disclosure herein should not be considered to be limited to a particular implant. According to one embodiment, a suitable implant may have a generally circular shape. However, implants having various other shapes may also be required depending upon the shape of the implant site. Implant sites having a non-circular shape may result when at least a portion of the cutting path of the cutting device does not contact the articular surface or bone. For example, if at the depth of the implant site the width of the articular surface is less than the cutting radius of the cutting device, an implant site may be provided having a truncated circular shape. Various other shapes of implant sites may result depending upon the profile of the articular surface at the depth of the implant and the radius of the cutting path of the cutting device used to excise the implant site.

Referring again to FIG. 7, an implant 58 according to the illustrated embodiment of the present disclosure may be provided having a load bearing surface 60 that may approximate the geometry or curvature of the articular surface being replaced by the implant. In one embodiment the geometry of the load bearing surface may be based on the actual articular surface being replaced. For example, mapping techniques known in the art may be used to measure the geometry of the region of the actual articular surface being replaced. An implant may then be constructed or selected from a set of implants having predetermined geometries. Alternatively, an implant for a specific application may be fabricated or selected from a set of standard sized/shaped implants to provide a general approximation of the articular surface being replaced. Selection or fabrication of an implant may rely on various degrees of quantitative reference to the articular surface being replaced, including no quantitative reference to the articular surface.

According to one aspect, the system herein may be used to provide information regarding the curvature of the articular surface 22. According to one embodiment, the curvature of the articular surface 22 may be measured or approximated using the locating hoop 12. The locating hoop 12 may contact the articular surface at a plurality of locations about the bottom circumference of the locating hoop 12 and/or continuously about the bottom circumference of the locating hoop 12. The height of the articular surface 22 in the center of the locating hoop 12 may be measured relative to the bottom circumference of the locating hoop 12, for example by using the probe-driver 46. Two generally opposed points of contact between the bottom circumference of the locating hoop 12 together with the radius of the locating hoop 12, and the height of the articular surface 22 generally in the center of the locating hoop 12 may define three points on a curve generally corresponding to the curvature of the articular surface. The geometry of the articular surface 22 may be mapped or approximated by developing one or more such curves approximating the curvature of the articular surface. A map or approximation of the curvature of the articular surface 22 may be used to select and/or fabricate an implant that may suitably replace a desired portion of the articular surface 22.

An implant 58 may be retained in an implant site by a variety of mechanisms. For example, the implant may include one or more features adapted to interact with the fixation element to retain the implant in the implant site. Consistent with the illustrated embodiment, the screw 44 may include an opening extending there through. At least a portion of the opening may be configured having a precision taper. The implant 58 may include a post 62 having a precision taper adapted to mate with the taper of the opening of the screw 44. The implant 58 may be retained in the implant site by inserting the tapered post 62 of the implant 58 into the tapered opening in the screw 44 and applying an axial pressure or impact to the implant 58, thereby seating the tapered post 62 in the tapered opening.

Various other features and methods may be used to retain the implant in the implant site. The implant and the fixation element may include interacting or cooperating features other than a tapered post and tapered opening. For example, the fixation element and implant may include conventional compression fits features, snap-fits, etc. In an embodiment that does not employ a separate fixation element, the implant may include a feature such as a barbed post that may engage the sides of the implant site and/or a hole drilled into, or through, the bone. Bone cement may additionally, or alternatively, be used to secure an implant in an implant site.

According to a related embodiment, the locating hoop 12 and tool support 14 may be removed after the guide pin 42 has been installed in the bone 20. As discussed above, the guide pin 42 may establish a reference axis for carrying out subsequent steps of an articular surface replacement procedure. For example, the guide pin may establish a reference axis for guiding a cored drill bit, described above. The cored drill may be used to provide a tunnel for a fixation element which may include an opening or a feature oriented in a predetermined relationship to the reference axis. According to one embodiment, the opening or feature in the fixation element may be used for positioning and aligning subsequent operations, instruments, and/or devices.

Turning to FIGS. 8 and 9, the versatility of an articular surface replacement system 10 a is illustrated. In the depicted embodiment the articular surface replacement system 10 a is shown positioned to replace at least a portion of an articular feature such as femoral head 102. As with the previously described embodiment, the system 10 a may generally include a locating hoop 12 a coupled in a predetermined orientation and alignment with a tool support 14 a by an arm 16 a. The tool support 14 a may, in turn, position a cannulated shaft 18 a in a predetermined orientation and alignment with the locating hoop 12 a.

Consistent with the illustrated embodiment, the biting features of the distal tip 36 a of the cannulated shaft 18 a may be especially useful for reducing or preventing undesired movement of the cannulated shaft 18 a relative to the femoral head 102, or a similar highly arcuate or angled surface. As also indicated in the illustrated embodiment, the articular replacement system 10 a may suitably be employed to replace a portion of a femoral head 102, or similarly configured joint, without reference to the axis of the neck of the joint. This aspect of the present disclosure may allow the amount of the articular surface being replaced to be minimized.

Referring to FIGS. 10 through 13, a further embodiment of the articular surface replacement system is illustrated. In the further embodiment, an articular surface replacement system consistent with the present disclosure may be used to access an articular surface, at least in part, by tunneling through an adjacent bone. In the illustrated embodiment, a portion of a glenoid articular surface 62 may be accessed through a portion of the humerus 20 a and the articular surface 22 thereof. For the purpose of clarity and the ease of understanding, the glenoid articular surface 62 and surrounding structure are only representationally depicted in a simplified manner, rather than being illustrated in the full and complete structure of the scapula. Similarly, the structure and relationship of the humerus and glenoid also representationally depicted, in an at least slightly exploded form, for the sake of clarity and illustration of detail. While the illustrated embodiment is depicted with reference to the head of the humerus and the glenoid articular surface, the system herein is susceptible to use in the context of various other bones, joints, and articular surfaces.

Referring first to FIG. 10, the system 10 a, generally including a locating hoop 12 a coupled to a tool holder (not shown) via an arm 16 a may be used to locate a cannulated shaft 18 a in a desired relationship to defect on the articular surface 22 a of the humerus 20 a, or on the glenoid articular surface 62 in a manner generally as described with reference to the preceding embodiment. Particularly, the locating hoop 12 a may be located surrounding, or in a desired relationship to, a defect in, or portion of, the articular surface to be replaced. Consistent with the illustrated embodiment, the defect or portion to be replaced may be located in either the articular surface 22 a of the humerus or in the glenoid articular surface 62. Consistent with an embodiment herein, a corresponding portion of each articular surface 22 a, 62 may be replaced.

As shown, with the locating hoop 12 a located in a desired relationship to the defect or portion of an articular surface 62 to be replaced, a guide pin 42 a may be drilled through the humerus 20 a an the articular surface 22 a thereof, using a cannulated shaft 18 a to orient and support the guide pin 42 a. The guide pin 42 a may provide a reference axis for carrying out subsequent procedures. According to one embodiment, the guide pin 42 a may be drilled at least a portion of the way into the glenoid articular surface 62 to mark the point of intersection of the reference axis with the glenoid articular surface 62.

Turning next to FIG. 11, after a reference axis has been provided through the humerus 20 a, an implant site 64 may be created in the glenoid articular surface 62. The implant site 64 may be provided by supplying a rotary cutter between the glenoid articular surface 62 and the articular surface 22 a of the humerus 20 a. The rotary cutter may include a socket or opening for receiving a drive shaft 65 therein. The drive shaft 65 may be provided extending through the humerus 20 a and may rotatably engage the rotary cutter between the articular surface 22 a of the humerus 20 a and the glenoid articular surface 62. The rotary cutter may be manually or mechanically rotatably driven and urged into the glenoid articular surface 62 to excise a region of the glenoid articular surface 62 and underlying bone. As would be expected, the rotary cutter may produce an implant site 64 in the glenoid articular surface 62 having a generally circular geometry.

Referring to FIGS. 12 and 13, after the implant site 64 has been excised, an implant 66 may be installed therein. Consistent with the illustrated embodiment, the implant 66 may have a generally circular cross-section and may have an outward face that may replace the excised region of the glenoid articular surface 62. The outward face of the implant 66 may be provided to generally correspond to the original glenoid articular surface 62, based on varying degrees of quantitative and/or qualitative comparison. Alternatively, or additionally, the implant 66 may have an outward face that is adapted to provide a desired interaction with a cooperating implant to be installed in the articular surface 22 a or the humerus 20 a. The implant 66 may be installed in the implant site 64 using a variety of techniques, including bone cement, separate fixation elements, one or more features on the implant to engage the walls of the excise site, etc., including combination thereof.

An implant site may be created in the articular surface 22 a of the humerus 20 a to provide an implant in the articular surface 22 a of the humerus 20 a that may interact with the implant 66 in the glenoid articular surface 62. Such an implant site may be created as described with reference to FIGS. 1 through 7. The implant site in the humerus 20 a may be provided either before or after the implant site 64 in the glenoid articular surface 62.

Various other features and advantages of the articular replacement system described herein will be appreciated by those having skill in the art. Similarly, the system disclosed herein is susceptible to numerous modifications and variations without materially departing from the spirit of the disclosure. 

1. An apparatus for retrograde access to an articular surface comprising: a locating device capable of being positioned on a portion of said articular surface; a guide capable of providing an axis relative to said locating device and through said articular surface, and an arm capable of coupling said locating device to said guide, said arm capable of maintaining a positional and angular relationship between said locating feature and said guide.
 2. An apparatus according to claim 1, wherein said locating device comprises a locating hoop having an opening capable of exposing a portion of said articular surface.
 3. An apparatus according to claim 1, wherein said locating device is capable of measuring a geometry of said articular surface.
 4. An apparatus according to claim 1, wherein said guide comprises a cannulated shaft.
 5. An apparatus according to claim 4, wherein an axis of said cannulated shaft intersects said locating hoop.
 6. An apparatus according to claim 4, wherein cannulated shaft is extensible from a tool support coupled to said arm.
 7. A method for replacing a portion of an articular surface comprising: locating a portion of said articular surface; forming a passage through bone behind said articular surface, said passage extending toward said articular surface; and excising an implant site on said articular surface relative to said passage.
 8. A method according to claim 7, wherein forming said passage through bone behind said articular surface comprises establishing a reference axis extending through said articular surface.
 9. A method according to claim 8, wherein said reference axis intersects said portion of said articular surface.
 10. A method according to claim 8, wherein establishing said reference axis comprises inserting a guide pin extending at least partially into said bone.
 11. A method according to claim 10, wherein forming said passage comprises drilling over said guide pin with a cored drill.
 12. A method according to claim 7, further comprising installing a threaded element at least partially into said passage, said threaded element having an opening extending therethrough.
 13. A method according to claim 12, wherein a depth of said implant site is controlled relative to said threaded element. 14 A method according to claim 8, wherein said implant site extends radially around said reference axis.
 15. A method according to claim 14, wherein excising said implant site comprises rotating a cutter about said reference axis.
 16. A method according to claim 7, further comprising installing an implant into said implant site.
 17. A method of accessing an articular surface comprising: positioning a locating device adjacent to a first articular surface; aligning a guide with said locating device, said guide providing an axis relative to said locating device; forming a passage through a second bone and a second articular surface of said second bone, said second articular surface facing said first articular surface; accessing said first articular surface through said passage.
 18. A method according to claim 17, wherein forming a passage through said second bone and said second articular surface comprises providing a reference axis extending through said second bone and said second articular surface and drilling a hole extending along said reference axis.
 19. A method according to claim 18, wherein providing said reference axis comprises inserting a guide pin extending at least partially into said second bone, said guide pin oriented along said reference axis.
 20. A method according to claim 17, wherein accessing said first articular surface comprises excising an implant in said first articular surface through said passage. 